About this project

OTGW-firmware is firmware for the NodoShop OpenTherm Gateway, which sits between an OpenTherm thermostat and boiler. The supported v2.0.0 configuration uses an ESP32-S3 LOLIN S3 Mini with the gateway's existing PIC co-processor; v1.x supported ESP8266 modules, but ESP8266 is no longer a v2 build target. The project builds with PlatformIO and can be flashed using the provided Python flasher or PlatformIO commands. The firmware decodes OpenTherm bus traffic, exposes it through a browser-based dashboard with live logs and graphs, and provides a REST API. MQTT support includes Home Assistant auto-discovery for more than 250 entities, covering temperatures, setpoints, modulation, flame status, hot water, faults, pressure, sensors, and SAT controls. A TCP serial bridge on port 25238 remains compatible with OTmonitor and Home Assistant's built-in OpenTherm Gateway integration. SAT (Smart Autotune Thermostat) is an embedded heating controller that can manage boiler flow temperature without relying on an external home automation controller. It combines weather compensation with a PID controller, automatic tuning, radiator/underfloor/heat-pump modes, presets, multi-zone temperature averaging, solar-gain compensation, summer suppression, pressure monitoring, and safety checks. It can use DS18B20 Dallas sensors, S0 pulse metering, and up to four Xiaomi LYWSD03MMC BLE sensors using BTHome v2 on ESP32. Other documented features include an SSD1306 OLED status display, Wi-Fi setup portal and AP fallback, optional W5500 Ethernet with failover, OTA firmware and filesystem updates, Telnet debug logging, webhooks, WebSocket live-log streaming, optional HTTP Basic Auth for protected settings/maintenance endpoints, and triple-reset credential recovery. A direct-GPIO ESP32 OpenTherm mode called OTDirect exists, including thermostat, boiler, gateway, monitor, and master+slave modes, while the direct-hardware board is described as prototype only. The README states that v2.0.0 is alpha software and directs production users to the 1.x branch or published releases. It also warns not to flash PIC firmware over Wi-Fi with OTmonitor, not to perform PIC upgrades while OTDirect is active, and to keep the device on a trusted local network rather than exposing it directly to the internet. The project is GPLv3-licensed, with third-party components retaining their stated licenses.